Haemolytic disease of the newborn

Excessive haemolysis (destruction of red blood cells) in the fetus and newborn by antibodies produced by the mother. Haemolytic disease of the newborn is most often caused by Rhesus incompatibility. This occurs when a mother with Rh-negative type blood, who has previously been exposed to Rh-positive blood through birth, miscarriage, abortion, or amniocentesis, is pregnant with a baby that has Rh-positive blood. Haemolytic disease has become uncommon since the introduction of routine preventative treatment for Rh-negative women during pregnancy (see anti-D(Rh₀) immunoglobulin). In mild cases of haemolytic disease, the newborn baby becomes slightly jaundiced during the first 24 hours of life (due to excess bilirubin in the blood) and slightly anaemic. In more severe cases, the level of bilirubin in the blood may increase to a dangerous level, causing a risk of kernicterus (a type of brain damage). Severely affected babies have marked anaemia while still in the uterus. They become swollen ( hydrops fetalis) and are often stillborn. In mild cases, no treatment is necessary. In other cases, the aim is to deliver the baby before the anaemia becomes severe, usually by induction of labour at 35–39 weeks’ gestation. If the baby is too young to be delivered safely, fetal blood transfusions may be necessary. After birth, phototherapy (light treatment that converts bilirubin in the skin into a water-soluble form that is more easily excreted from the body) can help to reduce jaundice. An exchange blood transfusion may be needed.